During the operation of a motor vehicle various offensive and/or unwanted noise, vibration and/or harshness (NVH) may arise. These offensive and/or unwanted NVH can originate in the vehicle engine, transmission, transfer case, front axle assembly, rear axle assembly, a forward tandem axle assembly, a rear tandem axle assembly or in other vehicle components. In a non-limiting example, offensive and/or unwanted NVH may originate in the vehicle engine due to the firing order of the cylinders, in axle assemblies due to axle gear mashing or by the rotation of unbalanced shafts. As a result, dampers are typically used in the automotive industry to reduce and/or cancel the offensive or unwanted NVH that is found in the vehicle.
Automotive manufacturers often require the use of one or more dampers near the transmission, transfer case, front axles, rear axles, forward tandem axles, rear tandem axles and/or rear drive units. As a result, one or more dampers are attached to various vehicle shafts such as a propeller shaft, a drive shaft and/or a cardan shaft. By locating the damper on the vehicle shaft it decreases the critical speed of the shaft. The critical speed is the speed or revolutions per minute (RPM) of the shaft which coincides with the natural resonate frequency of the shaft. Once the critical speed is reached, the shaft becomes unstable and ruptures. This reduces the safe operating speed or RPM of the vehicle shaft. As a result, it would be advantageous to attach a damper to a vehicle shaft assembly in a location where it will not reduce the safe operating speed or RPM of the vehicle shaft in the vehicle shaft assembly.
Additionally, attaching the damper on the vehicle shaft puts the damper in a location that is further from a constant velocity joint (CVJ) which results in an increase in the dynamic instability of the shaft assembly. This increases the amount of and/or the magnitude of NVH in the vehicle shaft that the damper needs to reduce and/or cancel which results in a decrease in the life-span of the damper. It would therefore be advantageous to attach a damper to a vehicle shaft assembly in a location that is not going to unnecessarily add to the amount of and/or magnitude of NVH that the damper needs to reduce and/or cancel.
Furthermore, most vehicle shafts require balancing as a step to reduce the amount of NVH in a rotating shaft. By attaching the damper to the vehicle shaft it makes it more difficult to properly balance the shaft. This results in an increase in the amount of steps and time to manufacture the vehicle shaft which increases the overall cost of the component. As a result, it would be advantageous to attach a damper to a vehicle shaft assembly in a location that will reduce the overall time and cost needed manufacture the vehicle shaft assembly.
Lastly, given the variations in the dimensions of the vehicle shafts it makes it difficult to mass produce dampers that can be attached to the various shafts of a vehicle. It would therefore be advantageous to attach a damper in a location where the tolerances for the vehicle component are tighter resulting in less variation in part dimensions and making it easier to mass produce the damper.